sex ratio

Cold storage is a valuable technique for extending the survival time of parasitoid wasps, but it may have a detrimental impact on their survival and successful oviposition. In this study, we investigated the effect of cold storage of the larval and pupal stages of Aenasius bambawalei at 4°C for two and four weeks on their post-storage developmental time, adult emergence and longevity, female sex ratio, and morphometric characteristics. The highest emergence rate (72%) was observed in pupae after two weeks of cold treatment. In females, the shortest (8.40 days) and the longest (11.40 days) developmental time were seen in pupae and larvae exposed to two weeks of cold treatment, respectively. This trend was also similar in males, and the pupae and larvae subjected to two weeks of cold treatment showed the shortest (10 days) and the longest (11.8 days) developmental period, respectively. The sex ratio and adult longevity decreased significantly with the increase of immature stages’ cold storage period. Additionally, the length of the hind tibia and antennae decreased compared to the control. Based on these findings, we recommend two weeks of A. bambawalei pupae cold storage to increase the survival time of the parasitoid, as cold storage of larvae as well as long period cold storage of pupae, may have negative effects on the adult's fitness.

Date palm borers are among the most important pests of date trees in Iran. This study aimed to determine the population fluctuations of rhinoceros beetles Oryctes sp., infesting the date palm Phoenix doctylifera, using light traps in Mahshar date palm orchards. Samplings were weekly conducted from 2021 to 2022 in two randomly selected date palm orchard. Over two years of monitoring coleopteran adults, two species of the genus Oryctes namely O. agamemnon mathiesseni and O. elegans were observed. The beginning seasonal activity of both univoltine species was middle May, reaching the peaks during summer, and the populations declined gradually till October. In each of research years, one of two species was dominant, so that in the first year, the number of adult beetles of O. agamemnon mathiesseni was significantly more than O. elegans, while in the second year, the number of O. elegans was higher. In both sampling years, the activity of dominant species in that year started earlier, and ended later. A two-year study of the sex ratio in these horned beetles revealed that females outnumbered males substantially (2.5 to 4 times in two years) in the subspecies O. agamemnon mathiesseni. For O. elegans, this ratio ranged from 1.5 times (2021) to 2.5 times (2022). The successful IPM programs are effectively dependent on prediction of the emergence time and population fluctuations of pest insects, and it is hoped that the results of this study will be useful to control of the rhinoceros beetles.

Field studies were carried out to evaluate the attractiveness of different food attractants viz. protein hydrolysate 10%, torula yeast 10%, yeast instant 7%, casein 5% and sugar molasses 10% towards the fruit fly, Bactrocera species in pear orchard. Different concentrations of food baits (as mentioned above) were prepared in 200 ml of water and transferred to locally designed traps made up of 1.5 liter cold drink plastic bottles. The traps were hung on fruit trees at a height of about 2 m and at appropriate distance from each other. No insecticide was used in the food attractants. Data were regularly recorded at weekly intervals on the total number of B. zonata or B. dorsalis captured their sex ratio and aggregate population density of both the species. Results showed that yeast instant attracted significantly higher population of B. zonata and B. dorsalis and hence the highest cumulative population of both species followed by treatment of sugar molasses and protein hydrolysate. Among all the treatments, torula yeast was found to be the least preferred attractant for B. zonata and B. dorsalis. Sex ratio (%) of B. zonata and B. dorsalis revealed that all the baits attracted significantly higher number of females than males with highest female percentage in protein hydrolyzate and the lowest in sugar molasses. The results showed that yeast instant, sugar molasses and protein hydrolysate were highly effective and could further be exploited in combination with certain chemicals to enhance their effectiveness and developing a strong fruit fly attractant.

Distribution of Harmonia axyridis as an invasive predator, newly appeared in Iran, was investigted in northern provinces of Iran. Some biological and morphological traits were studied, including color morphs, sex ratio, and adults body length. Samples were collected from four regions in north and east-north of Iran as well as two generations of Rasht population to assess the effect of geographical location and insect’s generation. Reproductive potential of females of two main color morphs (melanic and non-melanic) was also investigated in overwintering and summer generations. Sampling were succesful in Guilan, Mazandaran, Golestan, and North Khorasan. Proportion of melanic individuals in Heyran, Shaft, Bojnourd, Rasht (overwintering population), and Rasht (spring population) was 11.51, 12.64, 10.57, 12.17, and 11.63, respectively. Sex ratios ranged from 38 to 44% showing no difference among the obovevmentioned populations. Mean length of adult insect body in individuals from Bojnord (6.57±0.029 mm) was larger than others. There was no difference between females of the two main color morphs in terms of oviposition potential. However, overwintering females laid significantly more eggs than summer females, regardless of color morphs. This study confirmed progress of H. axyridis distribution towards new areas. Moreover, it was indicated that sampling location and generation have no effect on color morphs ratio in newly invaded areas, and oviposition rate cannot be a regulating factor for color morphs ratio in next generation.

The egg parasitoid wasp, Telenomus busseolae Gahan (Hym.: Platygastridae) is the most important natural enemy of sugarcane stem borers in sugarcane growing area of Khuzestan province. In order to know the parasitism rate of T. busseolae in plant crops compared with first ratoon crops an investigation was carried out in Amir-Kabir Agro-industry in southern Khuzestan. In this study six plant and six ratoon cane fields of commercial sugarcane cultivar, CP69-1062 was selected and sampling of sugarcane borers (Sesamia spp.) egg batches was made monthly from April to November. The results indicated that field age and sampling time has a significant effect on egg batch densities of sugarcane borers and parasitism of eggs by T. busseolae. The lowest egg batch density was observed in April and the highest was recorded in September both in plant crops and first ratoon crops. In plant crops the lowest egg parasitism rate (43.5 %) was observed in July, whereas the highest rate (84.4 %) was observed in April.  In the first ratoon crops the lowest rate of parasitism (38.8 %) was observed in June and then increased to 87.3 % in November. The percentage of adult emergence of T. busseolae was not significantly influenced by crop age and sampling time.There was no significant difference of progeny sex ratio in the two investigated crop ages, but sampling time significantly influenced on progeny sex ratio. The results of this study provide useful information on the population fluctuations of T. busseolae in plant and ratoon crops of sugarcane.

Mediterranean flour moth Anagasta kuehniella (Zeller) is considered as one of the hosts that used for mass rearing of Habrobracon hebetor Say (Hym.: Braconidae). In this research effects of five amounts of flour moth eggs (0.4, 0.5, 6.0, 0.7 and 0.8 gr) on a constant diet (1.5 kg of wheat flour and 0.5 kg of rice bran) and five amount of wheat flour that added as second feeding at the mid of rearing period (0, 0.25, 0.5 0.75 and 1 kg) were investigated on some larval morphological characteristics and sex ratio and fertility of adults moths. Results showed that maximum weight of 100 larvae (3.35 gr), was obtained in minimum amount of egg weight (0.4 gr) and maximum secondary feeding (1 kg). While, maximum total larvae weight in a treatment (254 gr), was recorded in 0.8 gr egg weight and 1 kg flour weight as secondary feeding. Also highest female/male sex ratio (1.29: 1) observed in 0.5 gr egg weight and zero secondary feeding. On the other hand, bigger larvae that reared on higher amount of flour, laid higher amount of eggs and their eggs were heavier too. According to results, for the best outcome in flour moth rearing in insectarium it would be suggested that at the beginning 0.4-0.5 gr of insect eggs should be added to 2 kg of rearing media and after that 0.8-1 kg of wheat flour should be added to this diet at the mid of rearing period.

The effects of the recommended dose (RD) and half of recommended dose (HRD) of four insecticides, abamectin, emamectin benzoate, acetamiprid and flubendiamide, were studied on different immature stages of Trichogramma evanescens, egg parasitoids of tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae). Parasitized eggs of the Angoumois grain moth, Sitotroga cereallela (Lepidoptera: Gelechiidae), were treated by the dipping method at the larval, prepupal, or pupal stages of the parasitoid. Cards containing 140 parasitized eggs of Sitotroga cerealella (Lepidoptera: Gelechiidae) were dipped into RD and HRD solutions of the insecticides for 10 seconds at each developmental stage of the parasitoid. Bioassay was performed only for immature stages of F0 generation. Reduction in emergence rate, parasitism rate and longevity of F0 generation as well as reduction in emergence rate and sex ratio of F1 generation were determined. Acetamiprid and flubendiamide were harmless at pupal stage, abamectin, emamectin benzoate and acetamiprid were slightly harmful but flubendiamide was harmless in regards of the emergence rate of the generation F1. Flubendiamide was the only insecticide with no significant difference on sex ratio compared to control. Both concentrations of abamectin and emamectin benzoate were slightly harmful and flubendiamide was harmless in terms of the rate of emergence and parasitism at the generation F0 in all developmental stages. In general, abamactin and flubendiamide in both generations were in slightly harmful and harmless groups, respectively.

Mass production of natural enemies has been considered a necessity for biological control programs. Most beneficial insects have a relatively short shelf-life, so suppliers do not have a sufficient number of biocontrol agents. The development of storage techniques for biocontrol agents provides flexibility and efficiency in mass production. Cold storage by prolonging insect development times provides a steady and sufficient supply of insects and synchronizes a desired developmental stage of biocontrol agents with times of pest outbreaks; so it reduces the cost of biocontrol programs by enlarging the production period over several months. Cold storage is usually associated with major fitness costs. Even if the insects remain alive after cold storage, a reduction of fitness may be observed, so the production of high quality natural enemies must be ensured. Developing effective methods is necessary in mass-producing. It has been reported that using fluctuating thermal regimes (FTR) (i.e. cold exposure interrupted by periodic short pulses of high temperature) versus constant thermal regimes (CTR) can progress the quality of biological control agents and significantly reduce rates of mortality. In this study, the impact of fluctuating thermal regimes versus constant low temperatures on the emergence rate, sex ratio, post-storage development time, adult size, egg load and egg size of the parasitoid wasp, Lysiphlebus fabarum (Marshall) was studied. The test was examined in three cold storage periods (1, 2, or 3 weeks). Lysiphlebus fabarum is an aphidiine parasitoid which attacks more than 70 species of aphids. Although both sexual (arrhenotokous) and asexual (thelytokous) populations of L. fabarum have been reported in Iran, the former population has been studied in this research. A stock colony of black bean aphid, Aphis fabae Scopoli (Hemi., Aphididae) was established from material collected in bean fields in Khuzestan province, Iran, in spring 2012. A sexual population of the parasitoid wasp, L. fabarum was collected from black bean aphids feeding on broad bean, Vicia fabae L. The synchronous cohort of L. fabarum was produced on the 2nd instar of aphid (at 21±1 ºC, 50–60% r.h., and L14:D10 photoperiod), then 30 two-day-old mated females were introduced into aphid colony consisting of 200 2nd instar individuals. The females were removed after 10 hours and parasitized aphids were reared for 54 hours (±6) to complete development to the late-instar larvae. These parasitized aphids, which were harboring late-instar larvae of wasp, were subjected to 6 ºC (as constant temperature regime) or were stored at 6 ºC with 2 hours daily exposure to 21±1 ºC (as the fluctuating temperature regime). The experiment was replicated with three cold storage periods (1, 2, or 3 weeks) with a control (direct development at 21±1 ºC). After completion of each storage temperature treatment, insects were transferred back to 21 °C until the emergence of adult wasps. Accordingly, the survival rate and the sex ratio (% females) were determined. The emerged wasps were then exposed to alcohol vapor for 2 minutes. The hind tibia of both gender was measured. Subsequently, the ovaries of each female were dissected to determine the egg load and egg size. According to results in CTR, survival of larvae was significantly reduced after one week of storage, and there was a gradual decrease in the second week, but there was no difference between survival of wasps that were stored after one and two weeks of storage. In FTR, emergence rate was decreased after one and two weeks of storage in comparison to the control, and the least survival was observed in the third week. When the survival was compared between different thermal regimes, FTR increased the survival in the first and second weeks, whereas after three weeks of storage there was no significant difference between two thermal regimes. In CTR, the least sex ratio of wasps was observed in those stored for two weeks, although there was no significant variation in sex ratios for control, one week and three week of storage. In FTR, cold storage did not affect on sex ratios of treatments. When the sex ratio was compared between different thermal regimes, for two and three weeks of storage, it was significantly higher in FTR and CTR, respectively. In females and males, larval storage increased development time relative to controls, in CTR. While in FTR, developmental time was decreased after two and three weeks of storage, in FTR. When developmental time was compared between two thermal regimes, post-storage development was slower in CTR after two and three weeks of storage in comparison to FTR, in both genders. In both thermal regimes, cold storage of wasps as larvae resulted in smaller male and female wasps relative to controls over all the storage periods. Egg load and egg size at emergence were progressively diminished as a function of the storage period, regardless of the thermal regimes. Egg load of wasps stored in CTR compared with FTR, was significantly higher for three weeks of storage. For all storage periods, egg size was significantly higher in FTR than CTR. Collectively, our results confirmed the beneficial effect of FTR relative to CTR, when larvae of L. fabarum were stored for two weeks at 6 °C. Although FTR reduced the development time, which could be a problem during delivery for mass release of natural enemies in the field, but the emergence rate, the sex ratio, the body size and the egg size were significantly higher in FTR than those in CTR. For three weeks of storage, FTR was more stressful than the CTR, as the wasps that were stored in CTR had significantly more post-storage development, sex ratio, body size and egg load than the fluctuating ones.

Biology and population growth parameters of Jasmine whitefly, Aleuroclava jasmini (Takahashi) were studied on four orange cultivars including Siavaraz, Valensia, Mars and Washangton under laboratory conditions (27 ± 1 oC, 60 ± 5% RH and 14: 10 h L: D). The mean immature developmental times of females on Siavaraz, Valensia and Mars were 31.38 ± 0.23, 28.43 ± 0.68 and 29.20 ± 0.67 days, respectively. A. jasmini survived only up to third nymphal instar on Washington cultivar. Immature mortality was 25.77 ± 0.43, 32.00 ± 0.29 and 32.00 ± 0.52% on the above cultivars, respectively. Mean sex ratios (percent of females) were 59.45 ± 0.45, 54.05±0.63 and 51.76 ± 0.44% on above mentioned cultivars, respectively. The mean females longevity was 3.40 ± 0.11, 5.15 ± 0.20 and 4.60 ± 0.22 days, respectively, on cultivars. Mean total fecundity was 25.53 ± 1.45, 40.00 ± 1.62 and 33.66 ± 1.87 eggs on cultivars, respectively. Intrinsic rate of increase (rm) was 0.055 ± 0.001, 0.065 ± 0.003 and 0.060 ± 0.002 number of female/female/ day and Net reproductive rate (R0) was 6.46 ± 0.51, 7.71 ± 0.54 and 11.41 ± 0.60 offspring/individualon the above mentioned cultivars. Finite rate of increase (λ) was 1.05 ± 0.001, 1.06 ± 0.003 and 1.07 ± 0.002 per days and Mean generation time (T) was 33.6 ± 0.221, 31.09 ± 0.435 and 31.69 ± 0.639 days on the above mentioned cultivars. Doubling time (DT) was 12.48 ± 0.106, 10.55 ± 0.186 and 9.02 ± 0.183 days on the above mentioned cultivars. Based upon the biological characteristics and life table parameters, Valensia was found to be the most suitable cultivars for development and reproduction of A. jasmini.

Egg parasitoids are the most important natural enemies of sunn pest, Eurygaster integriceps (Hem.: Scutelleridae). Knowledge on ecological requirements of natural enemies has essential role in success of applied biological control programs. One issue in this context is the effect of host embryogenesis upon performance of those wasps that developed within host eggs. This issue was studied by exposing new laid eggs (control), as well as one, two, three, four and five day old eggs to Trissolcus vassilievi. Two parasitoid populations were used in this study obtained from Tabriz and Varamin. Five day old eggs were rejected by the parasitoid except in six cases, all of which were allocated to male progeny. No significant difference was observed in the number of parasitized eggs between the two populations, but difference among host ages was significant. There was no significant difference in parasitism rate of wasps in ≤ 2 day old eggs, nevertheless significant decrease was observed in three and four day old eggs. Adult emergence rate, sex ratio (female%) and fecundity were influenced by host age. Fecundity significantly decreased by increasing host age over one day and a maximum 50% difference was recorded between control and four day old eggs. Those wasps that were developed in developed stages of host eggs were capable to partially compensate their initial lag in first week of the reproductive life. As a conclusion, host embryogenesis has little impact on the parasitoid fitness before two days, while more effects were observed in older eggs.

Biology of Jasmine whitefly، Aleuroclava jasmini (Takahashi) was studied on tangerine، orange، grapefruit، lime and sour orange under laboratory conditions (27±1oC، 60±5% RH and 14:10 L: D). The mean female immature developmental times on tangerine، orange، grapefruit and lime was recorded as 25. 62±0. 31، 28. 38±0. 34، 26. 74±0. 11 and 21. 76±0. 2 days، respectively. A. jasmini survived as far as first nymphal instar on sour orange. Mean sex ratios (female %) was 53. 32±2. 8، 59. 45±2. 04، 51. 67±1. 15 and 52. 41±2. 48% on above mentioned hosts plants، respectively. Mean immature mortality was 22. 59±1. 08، 26. 53±0. 73، 12. 34±0. 43 and 25. 25±0. 58%، respectively، on the same host plants. The mean adult longevity was 4. 51±0. 1، 3. 40±0. 12، 4. 23±0. 06 and 3. 64±0. 08 days for females، respectively، on the same host plants. Mean total fecundity was 30. 67±2. 41، 25. 53±1. 45، 31. 40±2. 63 and 38. 47±2. 09 eggs، respectively، on the same named host plants. Intrinsic rates of increase (rm) were 0. 093±0. 002، 0. 076±0. 002، 0. 091±0. 001 and 0. 101±0. 002 number of female/female/ day on the above mentioned host plants. Based upon the biological characteristics and life table parameters، lemon was found as the most suitable host for growth and reproduction of A. jasmini.

Biology of strawberry spider mite, Tetranychus turkestani Ugarov& Nikolski was studied on cucumber, courgette and melon under laboratory conditions (30±1oC, 70±5% RH and 14:10 L: D). The mean female immature developmental times on cucumber, courgette and melon were recorded as 7.73±0.14, 8.27±0.24 and 9.54±0.36 days respectively. The values of immature death rate were 42.31, 48.93 and 63.63% on the same three host plants. The average female life spans were estimated 5.78±0.51, 5.41±0.81 and 7.53±0.61 days on the same host plants. Mean daily egg counts were 3.31±0.61, 2.28±0.38 and 1.09±0.32 while mean total egg counts were recorded as 32.81±3.88, 18.5±4.56 and 14.04±2.35 eggs on the same named host plants. Mean sex ratios (female %) were 69, 85 and 78% on cucumber, courgette and melon, respectively. Intrinsic rate of increase (rm) were 0.272±0.01, 0.183±0.02 and 0.125±0.01 on the mentioned host plants. Based upon the biological characteristics and life table parameters, cucumber was found as the most suitable host for growth and reproduction of T. turkestani.

Ladybird Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae) has been reported from many parts of Iran, has an important factor on equilibrium and natural regulation of Acyrthosiphon pisum (Harris) (Hem.: Aphididae) population in alfalfa. Determining the population seasonal change of H. variegata and its parasitism rate by the most important parasitoid species was the aim of this study. The samplings were done from April to October, 2010 at research filed of Bu-Ali Sina University, Dastjerd (Hamedan Province) (ca. 4.5 ha of alfalfa var. Hamedani) where was intensively infested by Acyrthosiphon pisumHarris. Every week, H. variegata adults were collected by sweep netting and totally 400 samples were brought back to the laboratory. Population peakof H. variegata coincided with second and approximately third alfalfa cutting.The sex ratio of H. variegata (male: female) was calculated 1: 1.12. The most important parasitoid species of this predator was Dinocampus coccinellaeSchrank (Hym.: Braconidae) that its mean parasitism rate was %30.15 from September to November 2010. Therefore, considering nearly the permanent presence of this predator in alfalfa fields and necessity of conserving and supporting native ladybirds, this study showed the importance of H. variegata population change and some influencing factors.